Central air conditioner compressorsIt made the refrigerant flows!

Air conditioning compressor is the heart of the AC
units. It’s the mechanical components that use electricity and capacitor as the
single energy source to operate it.

The air conditioning compressor is the ac parts that
cause the refrigerant to flows in a cycle.

This compressor is not for residential, it is for commercial.

What
are the types of air conditioning compressors?

There are five main types of air conditioner compressors:

Reciprocating

Rotary compressor

Centrifugal compressor

screw compressors

Scroll compressors﻿

All five groups of HVAC compressors work
the same way, but their internal methods of compressing refrigerant vapors are
different.

The most common compressor is the reciprocating
compressor. It comes into two domes or housing:

Open
compressors

Hermetic
compressors

Hermetic compressor is the most common air
conditioner compressors found inresidential AC units and light
commercial units. So, the only compressor we’ll being focusing here is hermetic
compressors.

Hermetic compressor comes into two types:

Sealed or welded
hermetic compressors

Semi-hermetic (this
compressor has nuts and bolts holding it together.)

Sealed hermetic compressors

Welded hermetic compressors aka tin can or sealed
hermetic are throwaway compressors. There is no way of get inside the compressor, unless it’s cut open.

There’re few companies that open this compressor,
they are specialize in this kind of works. The compressors
manufacture opens the sealed hermetic compressors to examine it. Otherwise, it’s
a throwaway.

In sealed hermetic compressors the motor and
crankshaft are in vertical position. It used the suction refrigerant from the air
conditioner evaporator to cool the internal compressor at an operating
temperature.

The air conditioner compressors have a safety device
inside to protect the compressor from heating.

This device is internal overload. The air conditioning compressor is the
most expensive AC parts in condenser units; it’s wise to protect the
compressor.

In a hermetic compressor there’re two important
tubes that welded with the hermetic shell. These two tubes are:

Suction
line

Discharge
line

The suction line is the larger line connecting to
the indoor air conditioner evaporator. The AC compressors pull the
refrigerant through the suction line and releases it to the air conditioner
condenser through the discharge line.

In split-central air conditioner units, the suction
is always insulating to prevent the cool refrigerant from absorbing outside
heat.

Semi-hermetic
compressors

This is the air conditioning compressors that have
nuts and bolts. The motor and the compressor are inside the heavy iron cast.
This is the compressor that can be fixed by removing the bolts and shells that
holding it together.

This is commercial HVAC compressor, in residential,
it’s smaller.

There aren’t many residential that used these types
of compressor, but we could find it in larger home and light commercial. It can
be fixed in the field, if we have the necessary air conditioner equipment.

How
does a central air conditioner compressor works?

The HVAC compressors works by
using an electricity to energize the motor; which it turns cause compressor
crankshaft to rotates.

Reciprocating compressors are a piston-cylinder type
of pump. The main parts include a cylinder, piston, connecting rod, crankshaft,
cylinder head and valves. The operating cycle of a reciprocating compressor is
shown below.

On the down stroke of the piston, a low pressure
area is created between the top of the piston, the cylinder head and the
suction line of the air conditioning evaporator. Cold refrigerant vapor rushes
through the suction valve inlet and into the low pressure area.

On the up stroke, the suction valve closes and the
exhaust (discharge) valve is forced open with the increasing pressure. The
vapor is compressed and forced into the discharge (high) side of the
refrigeration system.

When the piston reaches the top of the cylinder, the
discharge valve closes, and the suction valve opens as the piston starts down
again drawing in cold refrigerant vapor to complete the cycle.

Note
that the connecting rod attached between the crankshaft and piston serves to
change rotary motion into reciprocating (back and forth) motion.

The piston rings prevent the vapor from escaping
between the piston and cylinder walls and improve the operating efficiency.

The compressor housing or crankcase contains the
bearing surfaces for the crankshaft and stores the oil that lubricates the
compressor parts.

The process of the air conditioning compressors are
showed between points 1 and 2 on the PH chart.

In split- central
air conditioner, the compressor is located outside within the condenser
units. It’s a vapor pump!

Compressors produce a pressure different between the
low side (suction pressure) and high sides (discharge pressure) of the
refrigeration system.

This is achieved by pulling of low pressure, low
temperature, superheated refrigerant vapor from the suction (evaporator) side.

It pulls the correct amount of refrigerant to fill
the volume. The refrigerant goes through the compressor, after it crosses
the compressor it then creates a high temperature, high pressure superheated
refrigerant vapor to the high pressure side (air conditioner condenser side).

The compression of the vapor causes the transfer of
heat energy to flows from the low side to the high side of the system.

As the air conditioning compressors compression the
refrigerant, additional heat is added to the refrigerant. These heats are:

Heat
of compression

Mechanical
friction heat

Compressors
winding heat

Other
suction line heat

The pressure different created by the operation of
the compressor is responsible for refrigerant flow through the refrigeration
cycle.